In vitro assay for pre-screening resistance to Fusarium Head Blight in durum wheat

SORESI, D.; ZAPPACOSTA D; GARAYALDE, A.; GARBUS, I.; MIRANDA R; ECHENIQUE V; CARRERA A

Roma

Congreso; International Symposium Genetics and Breeding of Durum Wheat; 2013

Fusarium head blight (FHB) caused by Fusarium graminearum is a serious wheat disease that produce considerable yield losses and micotoxin grain acumulation. Low genetic variability for resistance exists in durum wheat (Triticum turgidum L. ssp durum) germplasm. However, materials with resistance genes from T. turgidum spp. dicoccoides (Langdon (Dic-3A) and Lophopyrum elongatum (DGE-1) became recently available. Visual assessment of incidence and severity are the most common measures of disease intensity. In vitro assays have been proposed as alternative methods for screening resistance that entail earlier evaluation and more controlled experimental conditions. The objectives were to investigate the utility of an in vitro seedling assay for the identification of durum wheat resistant genotypes and to examine its relationship with severity. The assays were performed by using three sets of plant materials: i) six durum wheat commercial cultivars, ACA 1801F, Buck Platino, Buck Esmeralda, Bonaerense Inta Facón, Kofa and Ciccio and the line UC1113; ii) the durum cultivar Langdon and its derived resistant lines Langdon(Dic-3A) and Langdon-DGE-1and iii) the bread wheat cultivar ACA 601 and the derived resistant cultivar ACA 601Sumai3. Twenty seeds of each genotype were imbibed in a conidial suspension of F. graminearum or water in control. The experiment was performed three times (E1, E2 and E3). Six days after inoculation four variables were registered: percentage of germination, length and weight of coleoptiles, and weight of roots. Disease severity was estimated as the percentage of symptomatic spikelets/spike at 21 days post-inoculation. Mean comparisons between treatments and control samples using Student?s t-test, correlations within and among experiments, ANOVA based on MLGM and Fisher test among genotype means, multiple lineal regression on dependent severity variable were performed using Infostat and R Statistical Software. Differences among genotypes in the variables seed germination, coleoptile length and weight and root weight were observed. Based on the in vitro variables and according to Fisher significance a ranking of performance could be obtained. The introgressed genotypes showed better performance seedling assay and relatively lower damage in the spikes compared to the original varieties and other commercial cultivars whereas known susceptible genotypes positioned at lowest places. At the same time it was possible to assess the disease response for some novel promising cultivars, for which information about resistance is not yet available. Multiple regression analysis indicated that in vitro variables explained 71% of severity in E1, 51% in E2 and 74% in E3. The variables coleoptile length and coleoptile weight, consistently associated to severity, emerge as useful measures for predicting FHB resistance. This work proposes an in vitro assay for the evaluation of diseases susceptibility to FHB in durum wheat genotypes in a short time. The assay also constitutes a model system to study mechanisms involved in defense response of adult plants.